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BaseFieldControl.ErrorMessage property

Gets or sets a message indicating that, and possibly why, the current value of Value is invalid.

Namespace:  Microsoft.SharePoint.WebControls
Assembly:  Microsoft.SharePoint (in Microsoft.SharePoint.dll)

public string ErrorMessage { get; set; }

Property value

Type: System.String
A String representing the error message.

Implements

IValidator.ErrorMessage

The following is an example of an override of the Validate method that sets ErrorMessage. It first checks to see if the current control mode is Display, in which case it does not matter if the field is invalid because it cannot be changed anyway. The method also looks to see if the Value property is already known to be invalid by checking the IsValid property. If either of those checks is true, it does nothing. If neither is true, the method calls the base Validate which will set IsValid to false if it finds anything wrong with the Value property and set an appropriate ErrorMessage. (The BaseFieldControl.Validate method does nothing, so if the class whose Validate method is being overridden is derived directly from BaseFieldControl, then the call to the base Validate method can be omitted.) Finally, the method checks the value of Required and enforces that value.

public override void Validate()
{
    if (ControlMode == SPControlMode.Display || !IsValid)
    {
        return;
    }

    base.Validate();

    if (Field.Required && 
        (Value == null || Value.ToString().Length == 0))
    {
        this.ErrorMessage = Field.Title + " must have a value."
        IsValid = false;
        return;
    }
}

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